The present invention is an active microchannel fluid processing unit and method of making.
Miniaturized or small-scale fluid processing units, especially for multiple unit operations as chemical processing devices have been developed for military, automotive, and remote applications where size and weight limitations are important considerations. Typical applications include heating and/or cooling devices, fuel processors, and chemical synthesis units.
As shown in U.S. Pat. No. 5,611,214 entitled MICROCOMPONENT SHEET ARCHITECTURE, miniaturization is accomplished with micromachining microchannels onto a laminate. Laminates are stacked to form systems. This approach has also been shown in U.S. Pat. Nos. 4,392,632, 4,386,505, for refrigerators. U.S. Pat. No. 5,690,763 and WO 97/14497 (PCT/US96/16546) show microchannels on laminae for chemical processes. A disadvantage of this xe2x80x9claminatexe2x80x9d approach is the cost of the micromachining and the limited dimensions of the microchannels depending upon the type of micromachining process selected. More specifically, the dimension that is limited is the thinness of the fin between channels that may be achieved with machining. The machining forces necessarily require that the fin have sufficient thickness to withstand the machining process which may be thicker than a thermal optimal design.
An alternative form of xe2x80x9cstackedxe2x80x9d plates may be found in U.S. Pat. Nos. 5,455,401 and 5,620,616 for a plasma torch electrode. A stacked arrangement is also found in U.S. Pat. No. 5,016,707 for a multi-pass crossflow impingement heat exchanger.
Thus, the present state of the art offers the choices of multiple unit operations in a laminate structure that is expensive or single unit operation in a stacked structure that is less expensive. Accordingly, there is a need in the art for a method of making a fluid processing unit capable of multiple unit operations that is less expensive.
The present invention is an active microchannel fluid processing unit and method of making, both relying on having (a) at least one inner thin sheet; (b) at least one outer thin sheet; (c) defining at least one first sub-assembly for performing at least one first unit operation by stacking a first of the at least one inner thin sheet in alternating contact with a first of the at least one outer thin sheet into a first stack and placing an end block on the at least one inner thin sheet, the at least one first sub-assembly having at least a first inlet and a first outlet; and (d) defining at least one second sub-assembly for performing at least one second unit operation either as a second flow path within the first stack or by stacking a second of the at least one inner thin sheet in alternating contact with second of the at least one outer thin sheet as a second stack, the at least one second sub-assembly having at least a second inlet and a second outlet.
Each sub-assembly performs a unit operation. A unit operation is defined as an operation that changes the state of a working fluid including but not limited to condensation; evaporation; compression; pumping; heat exchanging; expansion; separation, for example solvent extraction, ion exchange, gas absorption, gas adsorption, distillation, phase separation, filtration; and chemical reaction, for example catalytic, non-catalytic, single phase (gas, liquid, plasma), and multiple phase. Two or more unit operations combined form a system operation. According to the present inventions, multiple unit operations as a minimum may be two (2) unit operations. Two unit operations may be achieved with a single fluid path or multiple fluid paths. For example, a single fluid may be pressurized then heated. Also, for example one fluid may undergo an exothermic chemical reaction followed by giving up heat to a second fluid. Although a heat exchanger has two fluids changing state and therefore may be considered two unit operations, a heat exchanger is defined herein as one unit operation, consistent with industry practice.
Systems include but are not limited to heat pumps, heat engines, thermochemical compressors, fuel cells, chemical synthesis units including pharmaceutical, and chemical purification units, analytical devices such as sensors, chromatographs and multiple catalyst screening tool. It will be understood that such systems may require only two or a few sub-assemblies performing at least two unit operations, or may require tens, hundreds or thousands of sub-assemblies performing at least two unit operations. It will be further understood that such systems may include components beyond the sub-assembly(ies) of the present invention, for example balance of plant.
An object of the present invention is to provide an active microchannel fluid processing unit capable of performing at least two unit operations. An advantage of the present invention is reduced cost of constructing a system or sub-system of two or more unit operations for fluid processing. Further advantages include elimination of gaskets or other sealing devices commonly used in high temperature/high pressure devices, and minimization of fluid interconnects because all liquids and gases involved in the process are confined within the as-built device. The stacking fabrication method of the present invention permits the formation and incorporation of complex microchannel arrays and headers within the completed device without the need for post-assembly machining.
The subject matter of the present invention is particularly pointed out and distinctly claimed in the concluding portion of this specification. However, both the organization and method of operation, together with further advantages and objects thereof, may best be understood by reference to the following description taken in connection with accompanying drawings wherein like reference characters refer to like elements.